Constant laval



UNITED STATES PATENT OFFICE.

CONSTANT LAVAL, OF NEW YORK, N. Y.

MANUFACTURE OF MIRRORS AND SIMILAR SILVERED-GLASS ARTICLES.

SPECIFICATION forming part of Letters Patent No. 242,338, dated May 31,1881.

Application filed January 13, 1881. (No specimens.)

articles, and promoting the brilliancy of the same.

It consists in a novel process of depositing an electroplate or coatingupon the silvered backs of glass articles, as will be hereinafterparticularly described.

In carrying out my invention I prepare a solution consisting ofdistilled water, nine hundred and sixty cubic centimeters, hydrosulphateof ammonia, (2NH H S,) 10 grains, which I designate solution No. 1.

I also prepare another solution, composed of blue vitriol, one hundredgrams; distilled water, four hundred and eighty cubic centimeters;hydrosulphate of ammonia, five grams; cyanide of potassium, livegramsthese ingredients to be thoroughly mixed in solution, which Idesignate solution No. 2.

Having these solutions ready, I take a mirror or other glass articlewhich has been previously coated with silver by any of the usualprocesses, and wash the back of the same with my solution No. 1, andthen immerse the article in a bath of my solution No. 2, which bath alsocontains a sheet of pure copper. I then, by means of a suitable galvanicbattery or other electrical generator, treat the immersed article andbath in' the usual manner pursued in electroplating for the space ofabout twenty-five minutes, when the silver coating of the article willbe found to have ac quired a firm metallic copper hacking. The processis then complete, and, as will be seen, is simple, cheap, and speedy,and in addition to re-enforcing and protecting the silver coatingcondenses the same and causes it to have a greater brilliancy than whenbacked by any other means of which I am cognizant.

The washing with the first solution has the effect of formingupon thesilver a coating of sulphide of silver and slightly corroding the silversurface, so that the electroplate will adhere firmly thereto, it beingotherwise liable to peel oif.

I do not limit myself to depositing copper upon the backs ofsilvered-glass articles, as other metals capable of eloctro-dcpositionmay be used, and in such case the solution No. 2 would be varied tocontain a salt of the metal to be deposited instead of blue vitriol, andthe bath should also contain a piece of the said metal instead ofcopper. The solution and means for clectro-deposition should, in fact,conform to the requirements of the metal to be deposited, according tothe known modes of electroplating.

I am aware that in a process of preparing articles to receive a metalliccoating by electro-depositiou such articles have been first coated witha solution of nitrate of silver and then treated withsulphureted-hydrogen gas, for the purpose of producing a surface ofsulphide of silver, upon which a copper coating .is electroplated, and Ilay no claim to such process. In my process a metallic surface isproduced by the precipitation of silver from the solution of gun-cottonand nitrate of silver, and the treatment with hydrosulphate of ammoniais for the purpose of slightly corroding this surface, so that thesubsequently deposited electroplate will adhere firmly thereto, it beingliable to peel off from a smooth base.

\Vhat I claim is' The process of depositing an electroplate upon thesilvered back of aglass article, substantially as described, the sameconsisting in first washing the back of the article in a solution ofdistilled water and hydrosulphate of ammonia, and then subjecting it toa process of electroplating, substantially as described.

In testimony whereof I have hereunto set my hand in the presence of twosubscribing witnesses.

CONSTANT LAVAL.

Witnesses:

HENRY EDER, J. A. RUTHERFORD.

